Polyoxometalates (POMs) are desirable in materials applications ranging from uses as catalysts in selective oxidn. reactions to mol.-like building blocks for the prepn. of new extended solids. Using an unprecedented approach involving high temp., molten salt methods, a fascinating series of salt-inclusion solids (SISs) that contain high nuclearity POMs was isolated for the first time. Cs11Na3(V15O36)Cl6 (1) was synthesized using the eutectic NaCl/CsCl flux (m.p. 493°) which serves as a reactive solvent in crystal growth and allows for the SIS formation. Its framework can be viewed as an ionic lattice composed of alternately packed counterions of Cl-centered [V15O36Cl]9- clusters (V15; S = 11/2) and multinuclear [Cs9Na3Cl5]7+ cations. In light of the structural anal., 1 was proven to be sol. in H2O giving rise to a dark green soln. that is similar in color to single crystals of the title compd. IR spectroscopy of the solid formed from fast evapn. of the soln. supports the presence of dissolved V15 clusters. Also noteworthy is the magnetization of 1 at 2 K, which reveals an s-shaped plot resembling that of superparamagnetic materials.